Burner system for consuming waste fuel

ABSTRACT

A burner system for consuming waste fuel comprises a combustion unit having at least three combustion chambers arranged concentrically around a variable speed conveyor screw for directing the waste fuel along a fuel consumption path through the combustion chambers; an air chamber surrounding the combustion chambers to facilitate preheating combustion air delivered to the combustion chambers and to facilitate insulating the combustion chambers against thermal losses to the environment; a boiler in fluid communication with the combustion chambers for heating fluid to facilitate an energy conversion process; and an intelligent control system for controlling operation of the burner system. The control system controls operating parameters of the boiler including pressure, temperature and fluid level and activates an emergency stop alarm if any one of the operating parameters is outside a predetermined range of operating values.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application based on Ser. No.13/572,663, filed on Aug. 12, 2012, which is a continuation-in-partapplication based on Ser. No. 12/367,462, filed on Feb. 6, 2009, nowU.S. Pat. No. 8,240,258. The disclosure of the base applications areincorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates generally to fuel burners, especiallyburners for waste fuel, such as waste plastic. Considerable researcheffort has been invested toward finding methods of converting wasteplastics to usable fuels as a means of plastic recycling. Waste plasticsare burned to generate heat, which may be used for water heating,industrial heat, or other purposes. Important considerations related towaste plastics as fuel sources are: maximizing energy by burning thesolid fuel completely, minimizing heat losses to the environment,compactness of the burner, and minimizing soot and harmful gasesemission.

Some existing waste fuel burners have multiple combustion chambers,which improve the completeness of the burning, but the combustionchambers are arranged one after another, therefore resulting in a longburner and significant heat losses due to the exposed outer surfaces.

Other existing waste fuel burners accumulate ash, soil, and sand duringthe burning process. These burners have to be periodically stopped forthe removal of accumulated non-combustible material.

There is therefore a need for solid waste burners that minimize burnersize and heat losses, while maximizing the completeness of fuel burning.The burner should also minimize soot and harmful gases emission, whilereducing the accumulation of the non-combustible material inside theburner.

BRIEF SUMMARY OF THE INVENTION

The present invention relates generally to burners that use solid fuels,especially waste plastic fuels. Burner size is minimized by havingmultiple combustion chambers arranged concentrically around a rotatingscrew conveyor. Heat efficiency is improved by having an air chamberdisposed around the combustion chambers, because the air for thecombustion is preheated prior to being delivered to the combustionchambers, while the air chamber at the same time thermally insulates thecombustion chambers against the environment. Waste plastic istransported from a fuel hopper to the combustion chambers by a rotatingscrew conveyor having spiraling auger blades. Speed of the screwconveyor rotation controls the consumption of waste plastic and, hence,the amount of thermal energy generated in the burner. Parts of thecombustion chambers can also rotate to auger waste plastic for betteroxidation, therefore enhancing the combustion process.

In one embodiment, a burner system for waste fuel, comprises 1) acombustion unit having a plurality of combustion chambers arrangedconcentrically around a single rotatable feed mechanism, wherein theindividual ones of said combustion chambers are in fluid communicationwith one another; 2) an air chamber surrounding the plurality ofcombustion chambers facilitates preheating combustion air delivered tothe plurality of combustion chambers and further facilitates insulatingsaid plurality of combustion chambers against thermal losses to theenvironment; and 3) a discharge chamber in fluid communication with theplurality of combustion chambers and a 4) boiler for heating waterand/or oil to facilitate an energy conversion process.

In one aspect of the above described embodiment, the single rotatablefeed mechanism is a variable speed conveyor screw for directing thewaste fuels along a fuel consumption path through the individual ones ofsaid plurality of combustion chambers; wherein the plurality ofcombustion chambers include a first combustion chamber, a secondcombustion chamber, and a third combustion chamber; wherein theplurality of combustion chambers are arranged radially one after anotherso that the combustion unit has an overall axial length in the directionof said variable speed conveyor screw; and wherein said variable speedconveyor screw has a longitudinal length that is about equal to alongitudinal length of an individual one the combustion chambers in theplurality of combustion chambers.

In another embodiment of the present invention, a burner system forwaste fuels comprises 1) a rotatable feed mechanism for directing thewaste fuel to a combustion unit; the combustion unit having first,second and third combustion chambers in fluid communication with oneanother and substantially coaxially arranged with respect to therotatable feed mechanism; wherein the first combustion chamber beingarranged to receive the waste fuel from the feed mechanism; an outletfor discharging exhaust materials from the third combustion chamber;wherein the combustion chambers have approximately like axial extentsand wherein the first through third combustion chambers are arrangedradially one after the other so that the combustion unit has an overallaxial length in the direction of the feed conveyor approximately equalto the length of an individual combustion chamber.

In one aspect of this another embodiment, the burner system includes acombustion air inlet orifice for each combustion chamber arrangedupstream of the respective combustion chambers.

In another aspect of the present invention, each combustion chamber isradially spaced apart from the other combustion chambers by inner andouter tubular walls.

In still yet another aspect of the present invention each combustionchamber is defined in part by a tubular wall that is common to twocombustion chambers.

In yet another aspect of the present invention, the burner systemincludes radially oriented end walls arranged between adjacentcombustion chambers and spaced apart from respective ends of the tubularwalls for generating an S-shaped flow of combustible materials,combustion air, smoke and particulates from the first through the thirdcombustion chambers.

In another aspect of the present invention, at least one of the endwalls is rotatably fixed to the feed mechanism for rotation with thefeed mechanism.

In yet another aspect of the present invention the burner systemincludes auger blades fixed to the tubular walls for rotation therewithfor advancing the combustible materials and products of combustionthrough the combustion unit.

In yet another aspect of the present invention the burner systemincludes auger blades fixed to the tubular walls for rotation therewithfor advancing the combustible materials and products of combustionthrough the combustion unit.

In another aspect of the present invention the burner system includesorifices located in the housing and communicating with the air flowpassage of the housing for directing combustion air from the air flowpassage in the housing to upstream ends of the combustion chambers.

In one aspect of the present invention, the feed mechanism of the burnersystem includes a screw conveyor having a hollow interior extendingaxially along the conveyor and into the combustion unit for directingcombustion air to the combustion unit, and one or more orifices disposedradially from the hollow interior and axially located on the screwconveyor so that the orifices discharge air to at least one combustionchamber.

In yet another aspect of the present invention, the burner systemincludes discharge blades attached with the feed mechanism for swirlingcombustion gases and flushing non-combustible material out of the burnersystem.

In still yet another aspect of the present invention, the burner systemincludes an auxiliary burner configured to start burning of the wastefuel.

In yet another aspect of the present invention, the auxiliary burner ofthe burner system is selected from a group consisting of an oil burner,a gas burner, a solid fuel burner, an electrical burner and combinationsthereof.

In another aspect of the present invention, the burner system includes afuel hopper configured to provide waste fuel to the feed mechanism.

In one aspect of the present invention, the fuel hopper comprises arotator configured to rotate substantially inside a rotator housing, therotator further comprising a plurality of rotator protrusions inclinedopposite from the direction of the rotator's rotation, thus reducing theincidence of waste fuel sticking to a rotator housing as waste fuelapproaches the feed mechanism.

In yet another aspect of the present invention, the rotator protrusionsof the burner system have substantially triangular shape.

In still yet another aspect of the present invention, the rotatorprotrusions of the burner system have substantially semicircular shape.

In yet another embodiment of the present invention, a burner system forconsumption of waste fuel, comprises 1) a screw conveyor configured torevolve around its longitudinal axis, the screw conveyor having alongitudinal hollow interior for air distribution and a plurality ofradially disposed air intake orifices connecting the hollow interior tocombustion chambers, thus providing air for combustion process; 2) oneor more auger blades disposed substantially spirally around a portion oflength of the screw conveyor, the auger blades being configured to movewaste fuel along the longitudinal axis as the screw conveyor revolves;3) a first combustion chamber disposed substantially centrally aroundthe screw conveyor and around at least one orifice connecting thelongitudinal hollow interior with the outer surface of the screwconveyor; 4) a second combustion chamber disposed substantiallyconcentrically around the first combustion chamber and configured toreceive burning waste fuel from the first combustion chamber, the secondcombustion chamber being in fluid communication with at least one airintake orifice disposed on a housing and configured to provide air forthe waste fuel burning; and 5) a third combustion chamber disposedsubstantially concentrically around the second combustion chamber andconfigured to receive waste plastic from the second combustion chamber,the third combustion chamber being in fluid communication with at leastone air intake orifice disposed on the housing and configured to provideair for the waste fuel burning.

In one aspect of this yet another embodiment of the present invention,the burner system includes discharge blades attached with a feedmechanism for swirling combustion gases and flushing non-combustiblematerial out of the burner system.

In another aspect of the present invention, the burner system includesan air blower configured to provide air for waste plastic burning.

In yet another aspect of the present invention, the burner systemincludes an auxiliary burner configured to start burning of wasteplastic.

In still yet another aspect of the present invention, the burner systemincludes another auxiliary burner configured to start burning of wasteplastic.

In yet another aspect of the present invention, the burner systemincludes a motor coupled to the screw conveyor for revolving the screwconveyor.

In another aspect of the present invention, the motor of the burnersystem is a constant speed motor.

In one aspect of the present invention, the constant speed motor of theburner system includes a chain drive engaging the screw conveyor.

In another aspect of the present invention, the motor of the burnersystem is a variable speed motor.

In yet another aspect of the present invention, the variable speed motorof the burner system is a direct drive motor.

In still yet another aspect of the present invention, the firstcombustion chamber of the burner system is adapted to increase air flowfor combustion of substantially all the burning waste fuel.

In yet another aspect of the present invention, the burner systemincludes an intelligent control system for controlling operation of atleast the screw conveyor, the one or more auger blades, the firstcombustion chamber, the second combustion chamber, and the thirdcombustion chamber.

In another aspect of the present invention, the intelligent controlsystem of the burner system includes an emergency stop circuit forstopping operation of the burner system.

In one aspect of the present invention, the burner system includes aboiler coupled to the third combustion chamber for heating water and/oroil in the boiler.

In still yet another embodiment of the present invention, a burnersystem for consuming waste fuel, comprises 1) a combustion unit havingat least three combustion chambers arranged concentrically around avariable speed conveyor screw for directing the waste fuel along a fuelconsumption path through said at least three combustion chambers; 2) anair chamber surrounding said at least three combustion chambers tofacilitate preheating combustion air delivered to said at least threecombustion chambers and to facilitate insulating said at least threecombustion chambers against thermal losses to the environment; a boilerin fluid communication with said at least three combustion chambers forheating water and/or oil to facilitate an energy conversion process; and3) an intelligent control system for controlling operation of thesystem, said control system for further helping to control operatingparameters of said boiler including pressure, temperature, and waterand/or oil level and for activating an emergency stop alarm if any oneof the operating parameters of said boiler is outside a predeterminedrange of operating valves.

In another aspect of present invention, the control system includessensors for helping to control the operation of a variable frequencydrive motor coupled to an auger rotatably feeding a waste fuel into saidcombustion unit, the auger being rotated at a non-operational speed, sothat the waste fuel is delivered at a lean rate; and for facilitatingthe operation of the variable frequency drive motor for feeding thewaste fuel into said combustion unit at an operational speed, so thatthe waste fuel is delivered at a run rate.

In yet another aspect of the present invention, control system furtherincludes sensors for facilitating the automatic operation of saidcombustion unit for a predetermined demonstration time to demonstrateoperation of the combustion unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood by reference to the detaileddescription in conjunction with the following figures, wherein:

FIGS. 1A and 1B show partial sectional plan and right views,respectively, of a first embodiment of the invention;

FIG. 2 shows a side sectional view of a second embodiment of theinvention;

FIG. 3 shows a detail sectional view a fuel supply unit;

FIG. 4 shows a side sectional view of a third embodiment of theinvention;

FIG. 5 shows a plan view of the third embodiment of the invention;

FIG. 5A shows a side sectional view of a fourth embodiment of theinvention;

FIG. 5B is a view along section line 5B-5B of FIG. 5A;

FIG. 6 shows a flow chart of an intelligent control system belonging tothe third and fourth embodiments of the invention;

FIG. 7 is a continuation of the flow chart of FIG. 6;

FIG. 8 is a further continuation of the flow charts of FIGS. 6-7; and

FIG. 9 illustrates a burner coupled to a vertical boiler, which burnerboiler system is constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1A, 1B, and 2, a burner system 1 for burning wastematerial, particularly waste plastic, has a feed mechanism 2 defined byan elongated transport or conveyor screw 4 provided with a central lumen6 extending substantially through the entire length of the conveyorscrew 4. The conveyor screw 4 is situated below an intake opening 8 ofthe feed mechanism and extends forwardly (to the right as seen in FIGS.1A and 2) to a combustion unit 10. The combustion unit 10 that isdefined by a plurality of concentric combustion chambers, indicatedgenerally at 11, include, for example, a first combustion chamber 12, asecond combustion chamber 14, and a third combustion chamber 16. Theplurality of combustion chambers 11 is coaxially disposed about conveyorscrew 4 at increasing radial distances from the conveyor screw 4. Thedownstream end of the third combustion chamber 16 is in fluidcommunication with a discharge section 18 of the burner system 1, whichreceives smoke and incombustible particulates from the plurality ofcombustion chambers 11 and discharges these materials from the burnersystem 1 into the atmosphere, via a nose cone 30′. A double walled outerhousing 20 defines an air passage 48, which surrounds a portion of theconveyor screw 4, the combustion unit 10 and the discharge section 18.

Feed mechanism 2 of burner system 1 includes the earlier mentionedconveyor screw 4 with spiral windings 5 and a generally tubular, doublewalled conveyer housing 22, which partially encloses the rotating screw4. A motor 24 drives a shaft 28 of the screw 4 via a chain 26. Othersuitable drives such as a gear drive, a belt drive or the like can beemployed, so there is no intention of limiting the disclosed inventionto only a chain driven shaft.

Intake opening 8 is arranged proximate to an upstream end of the screw 4(on the left as seen in FIG. 2) through which plastic waste or othermaterial is entrained for conveyance in a downstream direction (to theright as seen in FIG. 2) towards combustion unit 10. The downstream endof shaft 28 of screw 4 is free of spiral windings and extends into thecombustion unit 10 where it is suitably journaled.

Combustion unit 10, as already described, is formed by the threeconcentric combustion chambers 12, 14, 16, each of which has inner andouter radial boundaries that are concentric with the axis of shaft 28and interconnected by radially extending walls. In particular, theinside radial boundary of first combustion chamber 12 is defined by thearea bounded by the outer surface circumference area of conveyor shaft28. The outside radial boundary of first combustion chamber 12 isdefined by an interior surface area of an extension 30 of the tubularhousing portion 20 surrounding the conveyor screw 4. The inside radialboundary of second combustion chamber 14 is defined by the exteriorsurface area of the extension 30. The outside boundary of the secondchamber 14 is defined by a tubular wall 34 that is coaxial with andspaced apart from extension 30. An end wall 32 that is connected to andsubstantially perpendicular to tubular wall 34 is fixed to conveyorshaft 28 and is axially spaced from a downstream end of extension 30, soas to form a transition space between the first and second combustionchambers 12, 14. Finally, an exterior surface of tubular wall 34 definesthe inside radial boundary of third combustion chamber 16, while theoutside radial boundary of the third combustion chamber is formed by aportion of the inside interior surface area of housing 20, as best seenin FIGS. 1A and 2. The transition space between the second combustionchamber 12 and third combustion chamber 16 is provided by radial airpassage 47 of housing 20. The downstream end of the third combustionchamber 16 opens to the discharge section 18 of the burner system 1.

As is illustrated in FIG. 1A, gaseous material, particulates and thelike from first combustion chamber 12 move along an S-shaped line 38,past the second combustion chamber 14 and the third combustion chamber16, and into discharge section 18. As best seen in FIG. 1B, tofacilitate movement of the materials through the plurality of combustionchambers 11, a plurality of sets of auger plates 40, which arepreferably inclined relative to the axis of shaft 28 to help advance thematerials in a downstream direction, are suitably arranged on the innerradial surfaces of the first through third combustion chambers 12, 14,16. In the embodiment illustrated in FIG. 2, the auger plates for thefirst and third combustion chambers 12, 16 rotate with shaft 28, whilethe set of auger plates 40 for the second combustion chamber 14 arestationary. Alternatively, the plates for the second combustion chamber14 can be mounted on the inside of tubular wall 34 so that they, too,rotate with the shaft 28. Waste fuel, in particular, waste plastic fuel,introduced through intake opening 8, is moved in a downstream direction(to the right as seen in FIGS. 1A and 2) and it enters first combustionchamber 12. Auger plates 40 in the first combustion chamber 12distribute the material relatively evenly where it is liquefied,gasified and ignited by heat generated by flames and friction or heattransfer via tubular wall 34. The resulting partially combusted wasteplastic together with flames, smoke and other particulates generated inthe first combustion chamber 12 propagates in a downstream directionthrough second and third combustion chambers 14, 16 where the wasteplastic burns so that substantially only smoke, gaseous matter andnon-combustible particulates are then discharged into the dischargesection 18 of the burner system 1. Rotational discharge blades 19 swirlthe exhaust gas flow, thus improving a flush-out of the incombustiblematerials from the burner system 1. The discharge blades 19 whichprovide a sufficient swirling of the incombustibles may be made indifferent shapes. One example is a substantially propeller shapeddischarge blade.

A particular advantage provided by the waste burner system 1 of thepresent invention is that fresh combustion air is provided just upstreamof each of the combustion chambers 12, 14, 16. Complete incineration ofall the waste plastic takes time, thus feeding just sufficient air atthe upstream end of each chamber helps to sustain optimal combustiontherein. Optimal combustion, in turn, helps to maintain maximumtemperature in each chamber 12, 14, 16, because combustion air that isneeded further downstream in the process, namely in the second and thirdcombustion chambers 14, 16, does not travel through the combustionchamber 12 where it is not needed and need not be heated. In addition,the flow of relatively cool combustion air along the outside of thehousing 20 enhances energy efficiency because the air flow reduces heatlosses from the combustion unit 10 to the atmosphere, while at the sametime preheating the air needed for the combustion in the combustionchamber.

Referring now to FIG. 2, according to a second embodiment, air forincinerating waste plastics is supplied from a suitable source (orsources) at an air inlet 44, like, for example, a fan or a blower (notshown) used to enhance the air intake. Air next enters inner air passage46 defined by tubular double-walled housing portion 22. Some of the airin passage 46 is released into the space for conveyor screw 4 from anorifice 50, enters shaft lumen 6 via inlets 52, and continues to flow inthe direction of combustion unit 10, while simultaneously cooling theconveyor screw 4, thus increasing the reliability of the conveyor screw4 and its bearings. The remainder of the air in the annular inner airpassage 46 continues in a downstream direction and partially encirclesfirst combustion chamber 12. A radial air passage 47 fluidicallyconnects axially extending inner air passage 46 with axially extendingouter air passage 48, which surrounds combustion unit 10 and dischargesection 18 of the burner.

As shown in FIG. 2, air from the lumen 6 is discharged via first, secondand third sets of orifices 54 arranged, respectively, in the transitionspace between the first and second combustion chambers 12 and 14 andinto discharge section 18 of the burner, as is further described below.Additionally, the air needed for burning the waste plastic is separatelyintroduced into each of the three combustion chambers. Air flowing alongair passage 46 is discharged into an upstream portion of firstcombustion chamber 12 via orifices 56. A further set of housing orifices58 is arranged upstream of third combustion chamber 16 and extends fromair passage 46 into the transition space between the second and thirdcombustion chambers 14, 16. Instead of or in addition to orifices 58,radial air passage 47 can be provided with additional orifices such as,for example, orifices 60 located just upstream of third combustionchamber 16, as shown in FIG. 2. Air for the second combustion chamber 14is introduced by the first set of orifices 54 (located on screw 4) intothe transition space between the first and second combustion chambers12, 14 and therefore also upstream of the second combustion chamber. Theair flow through orifices 54, 56, 58 and 60 is suitably modulated tomatch the air flow rate to the amount of waste plastics introducedthrough intake opening 8.

To facilitate the incineration of waste plastic, particularly duringstartup operations, an auxiliary burner 62 in the transition spacebetween the second and third combustion chambers 14, 16 for heating allthree chambers, either directly (chamber 16) or indirectly (chamber 12via housing section 30 extending into the combustion unit and chamber 14via tubular wall 34). The auxiliary burner 62 may be oil burner, gasburner, solid fuel burner, or electrical heater. The inventors havefound that using the auxiliary burner for about 5 minutes preheats thewaste plastic sufficiently to efficiently start the combustion.

Referring now to FIG. 3, a waste plastic supply unit 150 can be attachedto the intake opening 8. Waste plastic is deposited in a fuel hopper151, wherefrom it is gravitationally fed into rotator housing 153. Agranular waste plastic GWP is illustrated in the fuel hopper 151, butother constitutions of the waste plastic are possible. Rotation of arotator 154 directs waste plastic towards the intake opening, andfurther toward the conveyor screw 4. The inventors have found that therotator protrusions 155 having a triangle or a semi-circular shape workwell, but other rotator protrusion shapes can also be used. Theinventors have also found that inclining the rotator protrusions 155 inthe direction opposite from the direction of their rotation minimizessticking of the waste plastic against the rotator housing 153.

Referring to FIGS. 4 and 5, there is shown an alternative or thirdembodiment of another burner system, generally referred to as 160. Theburner system 160 includes another embodiment of a combustion unit,generally referred to as 170. In this embodiment of combustion unit 170,nose cone 30 is eliminated. Elimination of nose cone 30 increases airflow within and exiting combustion unit 170. The increased air flow andexhaust allows combustion of substantially all solid fuels moved intocombustion unit 170 by conveyor screw 4. This ability to obtainsubstantially complete combustion of solid fuels substantially increasesenergy output of burner system 160 while reducing energy consumption andtherefore improving overall financial performance of burner system 160by about 50%.

Referring again to FIGS. 4 and 5, a variable frequency drive(hereinafter, VFD) motor, such as variable speed, direct drive motor 180is coupled to conveyor screw 4 for revolving or rotating conveyor screw4. The previously mentioned second embodiment burner 1 includes motor 24that drives shaft 28 of conveyor screw 4 by means of a chain 26.However, this alternative or third embodiment burner system 160 includesvariable speed, direct drive motor 180, rather than motor 24 of burner1. The direct drive and variable speed capability of motor 180 thatbelongs to alternative embodiment burner system 160 allows burner system160 to accommodate variable size and density of solid fuels.Accommodating variable size and density of solid fuels, in turn,increases capacity of burner system 160 and reduces energy consumptionof burner system 160. More specifically, direct drive motor 180increases overall efficiency by reducing energy consumption and allowsfor increased variances in fuel types, sizes and feed rates which, inturn, substantially increases overall energy output of burner system 160by over approximately 50%. In addition, direct drive motor 180 providesmore power to auger shaft 28 and therefore aids in releasing fuel thatmight otherwise stick or adhere to shaft 28. Also, the increased powerof direct drive motor 180 can increase speed of fuel feeding. Moreover,the increased power of direct drive motor 180 increases the capabilityof burner system 160 to efficiently accept dual fuel compositions, suchas waste plastic combined with liquid oil.

As best seen in FIG. 4, a second igniter or auxiliary burner 190 isprovided in addition to the first igniter or auxiliary burner 62. In amanner similar to location of auxiliary burner 62, second auxiliaryburner 190 is provided in the transition space between the second andthird combustion chambers 14, 16 for heating all three chambers, eitherdirectly or indirectly. A purpose of second auxiliary burner 190 is todecrease time needed to preheat combustion unit 170 and for theintroduction of a larger volume of liquid fuel that can be used inconjunction with solid plastic fuels. Decreasing time needed to preheatcombustion unit 170 and introducing a larger volume of liquid fuelincreases overall efficiency of combustion unit 170 by about 50%.

As best seen in FIG. 4, a pair of fuel injectors 65 and 165 is alsoprovided in the transition space between the second and third combustionchambers 14, 16 for amplifying the burning of the waste fuel tofacilitate increasing the energy output of the combustion unit 170. Inthis regard, a fuel, such as oil, or gas, is directly injected into thecombustion chambers to increase the burn rate of the waste fuel as itpasses through the third chamber 16. The fuel is supplied through fuellines from a secondary fuel source.

Referring to FIGS. 5A and 5B, there is shown an alternative or fourthembodiment of the burner system, generally referred to as 191. Burnersystem 191 is substantially similar to third embodiment burner system160, except a boiler 192 is included to heat a fluid, such as waterand/or oil, for any process requiring fluid of elevated temperature,such as in the case of district heating. In the case of districtheating, fluid (e.g., water) in boiler 192 will be heated by burningwaste fuel, such as waste plastic, and then pumped through insulated,underground or above-ground plumbing/pipes (not shown) to homes andbusinesses for use in space heating, water heating and industrialprocesses. Once energy from the heated fluid is used by the home orbusiness, the fluid can be returned to boiler 192 by means ofunderground or above-ground plumbing/pipes. Thus, such a piping systemwill be a closed-loop piping system (not shown). As an example ofanother application, boiler 192 may be configured to produce steam foruses such as generating electricity by passing the steam through asuitable turbine-generator (not shown). Alternatively, high pressure oil(e.g., thermal oil) for use in driving single or multiple turbines thatgenerate electricity. In one configuration, boiler 192 is coupled tocombustion unit 170 and is an annular cylinder defining a centrallongitudinal cavity 193 in which combustion unit 170 is disposed. Boiler192 and combustion unit 170 are coaxially aligned, as shown. An annularfluid chamber 194 is formed in boiler 192 and extends longitudinallysubstantially the entire length of boiler 192. A fluid inlet pipe P1 iscoupled to boiler 192 and is in fluid communication with fluid chamber194 for supplying the fluid to fluid chamber 194. In addition, a fluidoutlet pipe P2 is coupled to boiler 192 for exit of heated fluid (e.g.,water, water and/or oil, steam), as the case may be, from fluid outletpipe P2. It should be appreciated that the boiler 192 configuration thatis described herein comprises only one exemplary configuration forboiler 192, there being many possible configurations for boiler 192. Forexample, boiler 192 is shown as horizontally oriented. Alternatively,boiler 192 may be vertically oriented, if desired. Vertical orientationof boiler 192 may be desirable when horizontal space is limited.

It will be appreciated by a person of ordinary skill in the art of powergeneration that it is important to control operation of burner systems160, 191, so that burner systems 160, 191 perform at optimum efficiency,safely and with minimum operator intervention. Therefore, in order tosuitably control burner systems 160, 191, a computer apparatus 195includes an intelligent control system, generally referred as 200, asdescribed in detail hereinbelow. Intelligent control system 200 includesa plurality of sensors 205 (only one of which is shown) disposed inburner systems 160, 191 for sensing or measuring the operationalparameters of burner systems 160, 191, such as pressure, temperature,boiler fluid level, power generated, as well as other operationalparameters of burner systems 160, 191. With reference to FIGS. 4 and 5,burner system 160 does not include boiler 192, it being understood thatburner system 160 may include boiler 192 as an option, if desired.Sensing these operational parameters will allow an operator of burnersystems 160, 191 to monitor the operational parameters and takeappropriate corrective action should any one of the operationalparameters fall outside a permissible predetermined range of values.However, it will be appreciated that intelligent control system 200 willbe capable of automatically taking any necessary corrective action withminimum operator interaction. In addition, intelligent control system200, which will use a computerized software platform with an openarchitecture, is adapted to integrate therewith off-the-shelf,commercially available boiler vessel management systems. Such acommercially available boiler vessel management system may be of a typesuch as may be available from Tru-Steam Boilers & Services Pty Ltd,located in Chipping Norton, Australia.

In addition, intelligent control system 200 will provide substantiallycomplete control and monitoring of all burner mechanical and electricalcomponents, so that burner systems 160, 191 perform at optimumefficiency, safely and with minimum operator intervention. Intelligentcontrol system 200 will provide redundant safety capability forsubstantially all functional components of burner systems 160, 191. Acontrol panel (not shown) will also substantially enhance performance ofburner systems 160, 191 by providing operator or automatic control ofeach function of burner systems 160, 191. Integration and interfacedesign for boiler safety systems will virtually ensure burner systems160, 191 operate within predetermined and safe parameter ranges for apreselected boiler vessel, such as boiler 192. Also, intelligent controlsystem 200 will assist in enabling use of burner systems across a broadspectrum of applications including the ability to manage energy outputand use of various fuel types. It is believed that use of intelligentcontrol system 200 will increase overall performance of burner systems160, 191 by about 75%. The method of operation of intelligent controlsystem 200 is described hereinbelow.

Therefore, referring to FIGS. 6, 7 and 8, there is shown a flow chartillustrating the methods by which intelligent control system 200controls burner systems 160, 191. For purposes of brevity, the methodsby which intelligent control system 200 controls burner systems 160, 191will be described only with reference to burner system 191, it beingunderstood that the methods may apply to burner system 160, as well. Themethod of intelligent control system 200 starts at a step 1200 by theoperator of burner system 191 activating a power-on system step 1202.Activating power-on system step 1202 supplies electrical power tointelligent control system 200 and begins operation of burner system191. It should be appreciated by a person of ordinary skill in the artof power generation that power-on system step 1202 may include a “toggleswitch” (not shown) that energizes intelligent control system 200 whenplaced in a first position and de-energizes intelligent control system200 when placed in a second position.

As best seen in FIG. 6, power-on system step 1202 generates a signalthat is received by a decision step 1204. The decision step 1204determines whether an emergency stop (hereinafter “ESTOP”) circuit hasbeen energized. The ESTOP circuit (not shown) must be energized formotion devices to be powered and operational, such as previouslymentioned variable frequency drive motor 180 (i.e., VFD 180). The ESTOPcircuit may be either manually or automatically operated to shut-downburner system 191 in an emergency, such as might occur during boileroverpressure, based on a signal output from previously mentioned sensor205 (see FIG. 4). Referring to FIG. 6, the ESTOP circuit at step 1204 isenabled by a programmable logic circuit (hereinafter “PLC” circuit, notshown) output and preferably by two maintained pushbuttons (not shown).PLC instructions may be loaded into the PLC from a pre-programmedErasable Programmable Read Only Memory (EPROM, not shown) or anElectrically Erasable Programmable Read Only Memory (EEPROM, also notshown) included in the PLC. Also, one of the maintained pushbuttonsturns-on the ESTOP circuit to energize the ESTOP circuit and the othermaintained pushbutton turns-off the ESTOP circuit to de-energize theESTOP circuit. If the ESTOP circuit is not energized, then a “false”output signal (hereinafter a “no” output signal) is generated bydecision step 1204. The “no” output signal activates an ESTOP alarm at astep 1205. An output signal from the ESTOP alarm activated at step 1205continuously loops back to decision step 1204, whereupon decision step1204 again tests whether the ESTOP circuit has been energized. It shouldbe appreciated by a person of ordinary skill in the art of powergeneration that if the ESTOP circuit is de-energized (i.e., output fromdecision step 1204 is “no”), the PLC in the ESTOP circuit will detectthe condition and display the appropriate alarm message on a HumanMachine Interface panel (i.e., “HMI panel”, not shown) that may belocated in an operator control room (also not shown) associated withburner 160. However, if the ESTOP circuit is energized, then a “true”output signal (hereinafter “yes” output signal) is generated by decisionstep 1204. The ESTOP alarm is in an “on” state only upon depressing ofthe previously mentioned ESTOP push buttons or failure of PLC output. Ata step 1206, the “yes” output signal from the ESTOP circuit (i.e., fromstep 1204) is used to initiate a call subroutine step 1206, which callsthe “boiler ready” subroutine 1400 to verify that the boiler (see FIG.5A) belonging to burner 160 is ready to start operation. After the callstep 1206 has been executed, the program advances to an end step 1208,since the boiler ready subroutine 1400 is now being executed by theprogram. The boiler ready subroutine 1400 is best seen on FIG. 6.

Referring again to FIG. 6, when power is supplied to intelligent controlsystem 200 by activating the power-on system at step 1202, a continuouscheck subroutine 1300 is initiated which begins with a start step 1301.The system parameters comprise at least auger VFD, blower VFD, fuelfeeder VFD, safety controller alarm active, and fluid pump failed, whichparameters are detected, sensed or measured by previously mentionedplurality of sensors 205 (see FIG. 4). As shown in FIG. 6, when thecontinuous check of system parameters starts at step 1301, auger VFDfaulted is checked at decision step 1302. If auger VFD faulted is notactive, then a “no” signal is generated at decision step 1302 and thefault condition is checked again. The continuous check method does notproceed further, until a fault condition is detected at decision step1302 which, in turn, results in a “yes” signal and the method proceedsto a set alarms exist command step 1313.

The program then advances to a stop heat command step 1315 whichdisables the burner system 191. Next the system proceeds to a decisionstep 1317 to determine whether the burner system 191 has been disabledfor a predetermined number of minutes, where the predetermined number ofminutes is a sufficient number of minutes to allow the burner system 191to cool down. The program will loop at this decision step 1317 until thepredetermined number of minutes has elapsed. Once the predeterminednumber of minutes has elapsed, a yes condition exists and the programthen proceeds to the decision step 1204 and proceeds as previouslydescribed relative to that decision step 1204.

In FIG. 6, when the call boiler ready subroutine step 1206 is executed,the boiler verification subroutine 1400 begins at a start step 1401 toverify the boiler 192 is ready for operation. In this regard, the systemproceeds to a set of boiler ready decision steps 1402, 1404, 1406, 1408,and 1410 that will be described hereinafter in greater detail. Theverification begins at a pressure verification decision step 1402, andif the pressure of the boiler is not within a correct range, a “no”signal is generated which causes the program to advance to the commandstep 1313 where the program proceeds as previously described with a setalarms exist. If instead, the pressure is within range, a “yes” signalis generated allowing the program to advance to a boiler overtemperature decision step 1404. If the boiler 192 has an overtemperature condition, a “no” signal is generated which causes theprogram to advance to the command step 1313 where the program proceedsas previously described with a set alarms exist. If instead, the boilertemperature is within range, a “yes” signal is generated to permit theprogram to jump to the next decision step 1406 to verify that the firstboiler water level is sufficient. The terminology “water level” isintended to include “water and/or oil level” because the fluid in theboiler can be water alone or a combination of water and oil. If thefirst boiler water level is not sufficient, a “no” signal is generatedwhich causes the program to advance to the command step 1313 where theprogram proceeds as previously described with a set alarms exist. Ifinstead, the first boiler water level is sufficient, a “yes” signal isgenerated and the program goes to the next decision step 1408 to verifythat the second boiler water level is sufficient. If the second boilerwater level is not sufficient, a “no” signal is generated which causesthe program to advance to the command step 1313 where the programproceeds as previously described with a set alarms exist. If the secondboiler water level is sufficient, a “yes” signal is generated and theprogram advances to a decision step 1410.

Next, at the decision step 1410, the program detects whether the“disable heat sensor” is active. If it is active, a “yes” signal isgenerated and the system goes to the command step stop heat at step1315, where the system proceeds as described previously. If the disableheat active sensor is not active at decision step 1410, the programadvances to a call command to call the water ready subroutine 1600 thatwill be described hereinafter in greater detail. After the call command1412 is executed the program proceeds to an end step 1414 as the waterready subroutine 1600 will not be executed.

Turning now to FIG. 7, at a step 1601, the water ready call signal fromstep 1412 (see FIG. 6) is provided to a decision step 1602 that testswhether a call for heat signal is true or is energized. If the call forheat signal is not energized, then a “no” output signal is generated atdecision step 1602 and the decision step 1602 loops to again testwhether the call for heat is energized. If the call for heat signal isenergized, a “yes” output signal is generated. Similarly, in a logicalor other fashion with decision step 1602, another decision step 1603tests presence of whether the manual CFH (“Call for Heat”) signal istrue. If the manual CFH signal is not true, then a “no” output signal isgenerated at decision step 1603 and the decision step 1603 loops backand again tests for manual CFH signal. If the manual CFH signal is true,a “yes” output signal is generated at decision step 1603. The “yes”output signals from both the CFH signal energized at decision step 1602and manual CFH signal at decision step 1603 are passed to a decisionstep 1604 that determines whether water flow rate is acceptable.

Referring again to FIG. 7, if the water flow acceptable decision step1604 outputs a “no” signal, then a “watchdog” routine at step 1606generates a water pump failed alarm signal. A “watchdog” routine is acomputer software routine combined with sensor instrumentation thatperforms a timer action wherein multiple conditions are monitored. Ifthe monitored conditions are not valid for more than the timer duration,then the watchdog times-out and an alarm is activated. In this specificcase, an output signal from the watchdog routine at step 1606 thatgenerates the water pump failed alarm is passed to a call command 1608which calls the set alarms exist subroutine 1500 as best seen in FIG. 6.The program then proceeds to an end step 1610 since the set alarms existsubroutine 1500 will have been executed via a start set alarms existstep 1501. The start alarms exist step 1501 advances the program to theset alarms exists command 1313 where the program proceeds as previouslydescribed.

If the water flow acceptable decision step 1604 outputs a “yes” signal,then a set output to start blower VFD step is started at a step 1607 tofacilitate combustion. The process then advances from the command step1607 to a decision step 1609 to test whether a desired air flow isdetected in burner 160. If desired air flow is not detected, then a “no”signal is output from decision step 1609. The “no” signal is received bya watchdog routine 1611. This watchdog routine 1611 generates a blowerfailed to start alarm signal that is passed to the previously mentionedcall command 1608 where the program proceeds as previously described.However, if the output signal from the air flow detected decision step1609 is “yes”, then the “yes” output signal causes the program toadvance to a command step 1615 that sets an output to start a liquidfuel pump. The liquid fuel may be oil or kerosene and is used to aidcombustion. The output signal from command step 1615 is received at acommand step 1617 that, in turn, causes the output to generate an outputsignal to enable a safety controller (not shown). The program thenadvances to a call step 1619 which calls the safety controllersubroutine 1800 as best seen in FIG. 8. When the safety controllersubroutine 1800 has completed its execution, the program will return tothis point advancing to a decision step 1621 to determine whether thesafety controller output signal is active as will be describedhereinafter in greater detail.

Considering now the decision step 1621, when the safety controllersubroutine 1800 has been successfully executed and a safety controlleractive signal is generated, the call safety controller command 1619advances to the decision step 1621 via the return step 1815 enabling theprogram to advance. A safety controller active decision step 1621 testswhether the safety controller has started. If the output from safetycontroller active decision step 1621 is “no”, then a watchdog routine ata step 1623 produces the safety failed to start alarm and the method ofthe intelligent control system 200 then advances to step 1625 and ends.On the other hand, if the output signal from safety controller activedecision step 1621 is “yes”, then an instruction is generated at a step1627 to go to a step 1631. From step 1631, the program advances to acommand step 1631 which initiates a burner startup timer (not shown).The system then proceed to a decision step 1633 to determine whether thedelayed rotation of previously mentioned auger shaft 28 has elapsed fora predetermined time that is selected by the operator of burner 160. Ifoutput from decision step 1633 is “no”, then decision step 1633continuously loops and again tests whether the predetermined period oftime has elapsed. If the time period has elapsed, then decision step1633 passes a “yes” signal to a command step 1635 to set the output to“start rotation of auger shaft” routine at a step 1635. After the augershaft 28 starts rotating, the start rotation of auger shaft routine step1635 passes an output signal to a waste plastic fuel start decision step1637 that determines whether plastic fuel feed has started to feed fuelalong auger shaft 28 by means of previously mentioned auger plates 40.The decision step 1637 will cause the program to loop at this decisionstep until the waste plastic fuel feed starts. In this regard, when a“yes” signal is generated at decision step 1637, the system proceeds toa command step 1639 that sets the output to start the plastic feeder VFDmodulus or subroutine.

Once the command step 1639 has been executed, the program proceeds to acommand step 1641 which will set the plastic fuel feeder VHF speed to a“transition speed”. The program then goes to a decision step 1643. Atdecision step 1643, a determination is made by the system as to whethera liquid fuel bypass time delay has ended. The time delay in startingthe liquid fuel pump is provided to ensure that auger shaft 28 is infact rotating before starting the liquid fuel pump. If the liquid fuelbypass time delay has not ended, then a “no” output signal is producedby decision step 1643. Decision step 1643 loops and then again testswhether liquid fuel bypass time delay has ended. If the liquid fuelbypass time delay has ended, the method of intelligent control system200 executes a go to command step 1645 that advances the program to step1647 as best seen in FIG. 8.

Referring to FIG. 8, after the liquid fuel time delay that is tested atdecision step 1643 ends with a “yes” signal being generated, the programproceeds to a go to step 1645 that takes the routine to step 1647 asbest seen in FIG. 8. From step 1647, the program goes to a command step1649, which causes the system to set output to start a liquid fuel pump.However, operation of the liquid fuel pump is stopped at a command step1651 after the liquid fuel pump is started at step 1649. Stopping theliquid fuel pump after starting the liquid fuel pump confirms that theliquid fuel pump is operational. An output signal from the stop liquidfuel pump step 1651 is provided to initiate a plastic fuel feedervariable frequency drive (VFD) motor at a command step 1653. The speedof the VFD motor is set to a predetermined “lean rate” for feeding theplastic fuel at a predetermined, lower non-operational rate. The plasticfuel is fed at the lean rate for a predetermined time selected by theoperator of burner 160. During this time, the normal operating plasticfuel feed rate or “run rate” is delayed. The routine advances to adecision step 1655 that determines whether this time delay has endedbefore feeding the plastic fuel at the run rate. If the time delay forfeeding the plastic fuel at the lean rate has ended, then the plasticfuel VFD motor speed is set to the operational “run” rate at commandstep 1702 via a go to step 1657 that advances the program to step 1700,from where the program proceeds to the command step 1702.

Referring again to FIG. 8, an output signal from step 1702 is providedto a decision step 1704 to determine whether there is a “call for heat”.The call for heat is a PLC input point that is connected to atemperature switch, such as a thermostat. If the call for heat atdecision step 1704 is true, then a “yes” output signal is generated.This “yes” output signal is provided to a decision step 1706 thatdetermines whether an automatic stopping of a plant demonstration hascompleted. In this regard, operation of burner system 191 occasionallymay need to be demonstrated to interested parties, such as governmentregulators, investors and members of the public. When demonstration ofburner system 191 in an operating state is required, burner system 191is run only for a predetermined time. The predetermined time is set forthe time allowed for the demonstration. Therefore, burner system 191 isoperated until decision step 1706 determines that the allotteddemonstration time has elapsed. At that point, intelligent controlsystem 200 automatically stops operation of burner system 191 if thedemonstration time has elapsed by advancing to the stop heat command1315 as best seen in FIG. 6. Alternatively, if the call for heat atdecision step 1704 is false, then a “no” output signal is generated.This “no” output signal is not provided to the “demonstration” decisionstep 1706. Rather, this “no” output signal is provided to previouslymentioned stop heat step 1315.

Referring to FIGS. 4, 7 and 8, when the safety controller subroutine1800 is called at the previously mentioned call step 1619 (see FIG. 6),the safety controller subroutine 1800 begins at a start routine step1801. From the start step 1801, the operation of igniters 62, 190 (seeFIG. 4) are initiated at a command step 1802, that produces an igniteroutput signal indicating that igniters 62, 190 are operating. It shouldbe appreciated that the disclosure herein recites two igniters 62, 190;however, any number of suitable igniters may be used to initiate aflame. Next, the igniter output signals are received by an open liquidfuel solenoid (not shown) instruction at a command step 1804. Theigniter output signal of step 1802 in combination with the open liquidfuel solenoid instruction from step 1804 are passed to a decision step1806 to determine whether a flame is detected by an appropriate sensor205 (see FIG. 4), such as an ultraviolet photoeye and amplifier boardcombination (not shown). The ultraviolet photoeye and amplifier boardcombination may be of a type, such as a “C7027A1023 ULTRAVIOLETMINIPEEPER FLAME SENSOR”, that may be available from HoneywellInternational, Incorporated, located in Morristown, N.J., U.S.A. In thisregard, the “C7027A1023 ULTRAVIOLET MINIPEEPER FLAME SENSOR” is acompact flame detector for use with flame safeguard controls havingultraviolet amplifiers and detects ultraviolet radiation in flames. The“C7027A1023 ULTRAVIOLET MINIPEEPER FLAME SENSOR” is used with HoneywellFlame Safeguard primary safety controls for burners requiringultraviolet flame detection. Suitable operation of igniters 62,190 incombination with the proper operation of the liquid fuel solenoid shouldproduce a flame. However, if the flame is not detected within a “flameproving” time period, then the safety controller turns off its “valve”output signals in order to close the liquid fuel valves and turns on itsalarm output. If no flame is detected at decision step 1806, a “no”output signal is generated by decision step 1806. The “no” output signalgenerated by decision step 1806 is passed to decision step 1808 thattests whether the previously mentioned flame proving timing period haselapsed. If the output signal from decision step 1808 is “no”, then theoutput signal from decision step 1808 is passed back to decision step1806 and the presence of the flame is again tested. However, if theflame proving timing period has elapsed without presence of a flame,then decision step 1808 outputs a “yes” signal that is provided to asafety controller alarm at a step 1810. From the set safety controlleralarm output step 1810, the program advances to the return step 1813,where the program proceeds as previously described.

Referring again to FIG. 8, if a flame is detected at decision step 1806,the decision step 1806 outputs a “yes” signal that is provided to acommand step 1809 which sets a main valve out to enable solid fuel feed.Output from step 1809 is provided to a command step 1811 that sets asafety controller “active” input value that is supplied to previouslymentioned return step 1813 which returns the program to step 1621 viastep 1815 as described previously (see FIG. 7).

The pollution emission of one embodiment of the invention was tested bythe KTL (Korean Testing Laboratory, located in Seoul, Korea) bymeasuring harmful gas emissions during the waste fuel burning. Accordingto the tests, the dioxin level was 0.119 ng-TEQ/Sm3, the hydrogenchloride level was 0.78 ppm, and the sulfur oxides level was 6.60 ppm.Thus, these harmful gas emission levels were significantly below theKorean emission standard levels (dioxine: 5 ng-TEQ/Sm3, hydrogenchloride: 50 ppm, and sulfur oxides: 6.60 ppm), rendering the inventionenvironmentally friendly.

The above description is illustrative and is not restrictive, and, as itwill become apparent to those skilled in the art upon review of thedisclosure, the present invention may be embodied in other specificforms without departing from the essential characteristics thereof. Forexample, while the above invention is described in conjunction withplastic waste fuel, the embodiments of the present invention can also beused with other solid fuels, waste or not, like, for example, coal, sawdust, wood chips, or a mixture of solid fuels. Furthermore, while threecombustion chambers are described, a different number of combustionchambers may be used. These other embodiments are intended to beincluded within the spirit and scope of the present invention. The scopeof the invention should, therefore, be determined not with reference tothe above description, but instead should be determined with referenceto the following and pending claims along with their full scope ofequivalents.

The invention claimed is:
 1. A burner system for consuming waste fuel,comprising: a combustion unit having at least three combustion chambersarranged concentrically around a variable speed conveyor screw fordirecting the waste fuel along a fuel consumption path through said atleast three combustion chambers; an air chamber surrounding said atleast three combustion chambers to facilitate preheating combustion airdelivered to said at least three combustion chambers and to facilitateinsulating said at least three combustion chambers against thermallosses to the environment; a boiler in fluid communication with said atleast three combustion chambers for heating a fluid to facilitate anenergy conversion process; and a control system that checks operatingparameters of said boiler including pressure, temperature and fluidlevel and activates an emergency stop alarm if any one of the operatingparameters of said boiler is outside a predetermined range of operatingvalues.
 2. The burner system according to claim 1, wherein said controlsystem controls speed of a variable frequency drive motor coupled to anauger rotatably feeding a waste fuel into said combustion unit, theauger being rotated at a non-operational speed, so that the waste fuelis delivered at a lean rate; and facilitates the operation of thevariable frequency drive motor for feeding the waste fuel into saidcombustion unit at an operational speed, so that the waste fuel isdelivered at a run rate.
 3. The burner system according to claim 1,wherein said control system automatically operates said combustion unitfor a predetermined demonstration time.